In the manufacture of an aluminum hard disc, a glass disk, a wafer, a photo mask, or a liquid glass substrate, or the like, there is carried out a precise polishing, the so-called polishing process, using various grits, such as silicon oxide, alumina, ceria, in order to finish the surface thereof with extremely high precision. After the polishing step, abrasive grains and dust have adhered to the surface of a polished article. Then there is in need of a through clean in order to remove them.
Although there is ultrasonic cleaning or cleaning process using water jet, scrub cleaning with a sponge roller of polyvinyl acetal porous material is more commonly employed in order to attain great cleaning effect or to cause less damage to the substrate. Additionally, as a cleaning fluid, not only DI water but also various chemicals, such as acid, alkali, solvent, suitable for respective substrates, are used. As a cleaning fluid for a silicon wafer, for example, a mixture of ammonia water and oxygenated water, a mixture of diluted hydrofluoric acid, hydrochloric acid and oxygenated water, and the like are known.
Among sponge rollers of polyvinyl acetal porous material, a cylindrical brush roller having many projections on the circumferential surface thereof is commonly used for the cleaning, where the tops of the projections are continuously in contact with the surface of an article to be cleaned while the sponge roller is being rotated so that good cleaning effect is achieved (see U.S. Pat. No. 4,566,911). Since the contacts with the article to be cleaned are made only in the projections, there are, in comparison with a sponge roller having a smooth surface, advantages such as less friction, less damage to the article to be cleaned, or an advantage that dirt is readily passing thorough between the projections together with the cleaning fluid and thus removed from the article to be cleaned.
In a cleaning process respective dedicated cleaning devices for each of substrates are usually used. In any of the devices, it is common to rotate a sponge roller together with a core, which is connected to a rotation driver and around which is covered with the sponge roller, while the tops of the projections of the roller are made contact with an article to be cleaned.
In some devices a cleaning fluid is supplied through a nozzle or the like onto the upper portion or side of an article to be cleaned or a sponge roller, and it is practically carried out to supply the cleaning fluid into the sponge roller from the inside of the core so as to enhance the cleaning capability. In the latter case the core in a cylindrical shape has a hollow, and the cleaning fluid is introduced at one end of the core and then supplied into the sponge roller through holes communicating between the hollow portion and the outer surface of the core, and then flows out onto the outer surface of the sponge roller.
In U.S. Pat. No. 6,240,588 there is disclosed a brush core characterized by having a first plurality of holes aligned along a line in an axial direction of the core and a second plurality of holes aligned along a line in an axial direction of the core, where the first plurality of holes being located to offset relative to the second plurality of holes, the first plurality of holes and the second plurality of holes are alternately repeated around the core, and the first plurality of holes and the second plurality of holes are located in the channels recessed in the outer surface of the core. The bore defined through a middle of the core has a diameter of 0.060˜0.35 inches (1.524˜8.89 mm).
In U.S. Pat. No. 6,543,084 there is disclosed a brush core comprising an elongated member, the elongated member having a plurality of fluid discharge surfaces around and spaced from the central axis thereof, the plurality of fluid discharge surfaces being spaced from one another, and the elongated member has a fluid supply bore at its center with a diameter of 0.060˜0.35 inches (1.524˜8.89 mm), the elongated member having a plurality of holes communicating between the fluid supply bore and the fluid discharge surfaces. The plurality of holes communicating between the fluid supply bore and the fluid discharge surfaces each have a diameter of 0.005˜0.092 inches (0.127˜2.34 mm).
In U.S. Pat. No. 6,308,369 there is disclosed a brush assembly in a wafer cleaning system comprising a brush core having channels cut into the surface in an axial direction, a first cylindrical sleeve being concentric with the brush core, and a second sleeve (a brush body), the channels allowing a fluid to flow in an axial direction and then to the first and second sleeves.
In U.S. Pat. Nos. 6,247,197 and 5,806,126 there are disclosed devices having a cleaning brush mounted thereon.
In the conventional devices, however, there was a problem that the supply of a cleaning fluid from a core to a sponge roller was extremely nonuniform, and thus it was difficult to flow out the cleaning fluid evenly over the outer surface of the roller.
Furthermore, in the cleaning step a plurality of different types of cleaning fluid are often used in turn, and when the cleaning fluid in use is changed to another cleaning fluid, there is a problem that the cleaning fluid previously used remains in the bore of a core or in a cleaning sponge roller, and it took a long time to change the cleaning fluids.